航海英语天文航海章节练习(2017.12.26)

单项选择题
A star that suddenly becomes several magnitudes brighter and then gradually fades is a（）.
A.double star
B.variable star
C.nova
D.nebula
单项选择题
During one synodic rotation，a body makes one complete turn relative to the（）.
A.Earth
B.Sun
C.stars
D.vernal equinox
单项选择题
In the navigational triangle，the angle at the elevated pole is the（）.
A.meridian angle
B.altitude
C.right ascension
D.azimuth angle
单项选择题
Apparent altitude is sextant altitude corrected for（）.
A.parallax and personal error
B.inaccuracies in the reading and reference level
C.visibility and magnitude
D.All of the above are correct
单项选择题
Mars will not be visible（）.
A.at elongation angles near 180°
B.from quadrature to opposition
C.at conjunction
D.at opposition
单项选择题
In low latitudes，a first quarter Moon will always rise at about（）.
A.sunrise
B.1200 LMT
C.sunset
D.2400 LMT
单项选择题
In general，the most effective period for observing stars and planets occurs during the darker limit of（）.
A.sunset
B.civil twilight
C.nautical twilight
D.astronomical twilight
单项选择题
A correction for augmentation is included in the Nautical Almanac corrections for（）.
A.the Sun
B.the Moon
C.Venus
D.None of the above
单项选择题
A double star is a star that（）.
A.has a declination equal to twice that of the Sun
B.comprises two stars that appear close together
C.is twice as bright as a single star
D.suddenly becomes much brighter and then fades
单项选择题
A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has（）.
A.error of perpendicularity
B.side error
C.prismatic error
D.centering error